Storm van's Gravesande Karin, Layne Matthew D, Ye Qiang, Le Louis, Baron Rebecca M, Perrella Mark A, Santambrogio Laura, Silverman Eric S, Riese Richard J
Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
J Immunol. 2002 May 1;168(9):4488-94. doi: 10.4049/jimmunol.168.9.4488.
Cathepsin S is a cysteine protease with potent endoproteolytic activity and a broad pH profile. Cathepsin S activity is essential for complete processing of the MHC class II-associated invariant chain within B cells and dendritic cells, and may also be important in extracellular matrix degradation in atherosclerosis and emphysema. Unique among cysteine proteases, cathepsin S activity is up-regulated by IFN-gamma. Given its importance, we sought to elucidate the pathway by which IFN-gamma increases cathepsin S expression. Our data demonstrate that the cathepsin S promoter contains an IFN-stimulated response element (ISRE) that is critical for IFN-gamma-induced gene transcription in a cell line derived from type II alveolar epithelial (A549) cells. IFN response factor (IRF)-2 derived from A549 nuclear extracts associates with the ISRE oligonucleotide in gel shift assays, but is quickly replaced by IRF-1 following stimulation with IFN-gamma. The time course of IRF-1/ISRE complex formation correlates with increased levels of IRF-1 protein and cathepsin S mRNA. Overexpression of IRF-1, but not IRF-2, markedly augments cathepsin S promoter activity in A549 cells. Furthermore, overexpression of IRF-1 increases endogenous cathepsin S mRNA levels in 293T epithelial cells. Finally, freshly isolated bone marrow cells from IRF-1(-/-) mice fail to up-regulate cathepsin S activity in response to IFN-gamma. Thus, IRF-1 is the critical transcriptional mediator of IFN-gamma-dependent cathepsin S activation. These data elucidate a new pathway by which IRF-1 may affect MHC class II processing and presentation.
组织蛋白酶S是一种具有强大内切蛋白水解活性和广泛pH值范围的半胱氨酸蛋白酶。组织蛋白酶S的活性对于B细胞和树突状细胞内MHC II类相关恒定链的完全加工至关重要，并且在动脉粥样硬化和肺气肿的细胞外基质降解中可能也很重要。在半胱氨酸蛋白酶中独一无二的是，组织蛋白酶S的活性受γ干扰素上调。鉴于其重要性，我们试图阐明γ干扰素增加组织蛋白酶S表达的途径。我们的数据表明，组织蛋白酶S启动子包含一个干扰素刺激反应元件（ISRE），该元件对于源自II型肺泡上皮（A549）细胞的细胞系中γ干扰素诱导的基因转录至关重要。在凝胶迁移实验中，来自A549核提取物的干扰素反应因子（IRF）-2与ISRE寡核苷酸结合，但在用γ干扰素刺激后很快被IRF-1取代。IRF-1/ISRE复合物形成的时间进程与IRF-1蛋白和组织蛋白酶S mRNA水平的增加相关。IRF-1而非IRF-2的过表达显著增强A549细胞中组织蛋白酶S启动子的活性。此外，IRF-1的过表达增加了293T上皮细胞中内源性组织蛋白酶S mRNA的水平。最后，来自IRF-1（-/-）小鼠的新鲜分离的骨髓细胞在对γ干扰素的反应中未能上调组织蛋白酶S的活性。因此，IRF-1是γ干扰素依赖性组织蛋白酶S激活的关键转录调节因子。这些数据阐明了IRF-1可能影响MHC II类加工和呈递的新途径。
